Feat: Translation

routes/ai/index.ts

@@ -3,6 +3,7 @@ import { summarizeComments } from "./summarizeComments";
 import { filterPosts } from "./filterPosts";
 import { createEmbedding } from "./createEmbedding";
 import { askQuestion } from "./askQuestion";
+import { translate } from "./translate";
 
 export default {
   "/api/ai/summarizePostDetails": {
@@ -11,6 +12,9 @@ export default {
   "/api/ai/summarizeComments": {
     POST: summarizeComments,
   },
+  "/api/ai/translate": {
+    POST: translate,
+  },
   "/api/ai/filterPosts": {
     POST: filterPosts,
   },

routes/ai/translate.ts

@@ -0,0 +1,103 @@
+import { z } from "zod";
+import { verifySubscription } from "../../middleware/subscription";
+import { aiClient } from "../../utils/models";
+import { ai_provider } from "../../utils/models";
+import { generateText } from "ai";
+import { AIUsage } from "../../services/AIUsage";
+
+const translateSchema = z.object({
+  customerId: z.string(),
+  type: z.enum(["post", "comment"]),
+  sourceLanguage: z.string(),
+  targetLanguage: z.string(),
+  // Post-specific fields
+  postTitle: z.string().optional(),
+  postText: z.string().optional(),
+  // Comment-specific field
+  comment: z.string().optional(),
+});
+
+const systemPrompt = `You are a helpful assistant that translates text. Translate the given text accurately while preserving the original meaning, tone, and context. Only provide the translation without any additional explanations or formatting.`;
+
+const LANGUAGE_NAMES: Record<string, string> = {
+  auto: "automatically detected language",
+  en: "English",
+  "zh-Hant": "Chinese Traditional",
+  "zh-Hans": "Chinese Simplified",
+  es: "Spanish",
+  fr: "French",
+  de: "German",
+  pt: "Portuguese",
+  ja: "Japanese",
+  ko: "Korean",
+  ru: "Russian",
+};
+
+const getLangName = (code: string) => LANGUAGE_NAMES[code] ?? code;
+
+const makeUserPrompt = (
+  sourceLanguage: string,
+  targetLanguage: string,
+  type: "post" | "comment",
+  postTitle?: string,
+  postText?: string,
+  comment?: string,
+) => {
+  const sourceLangName = getLangName(sourceLanguage);
+  const targetLangName = getLangName(targetLanguage);
+
+  if (type === "comment") {
+    return `Translate the following comment from ${sourceLangName} to ${targetLangName}:\n\n${comment}`;
+  }
+
+  return `Translate the following Reddit post from ${sourceLangName} to ${targetLangName}:
+
+Title: ${postTitle}
+
+${postText ? `Post Content:\n${postText}` : ""}`;
+};
+
+let MODEL_ID: string = "";
+
+if (ai_provider == "groq") {
+  MODEL_ID = "openai/gpt-oss-20b";
+} else {
+  MODEL_ID = process.env.OPENAI_SUMMARY_MODEL || "gpt-4.1-mini";
+}
+
+export async function translate(req: Request) {
+  const body = await req.json();
+  const { customerId, type, sourceLanguage, targetLanguage, postTitle, postText, comment } =
+    translateSchema.parse(body);
+
+  const isSubscribed = await verifySubscription(customerId);
+  if (!isSubscribed) {
+    return new Response("Customer is not subscribed", { status: 403 });
+  }
+
+  const isOverLimit = AIUsage.isOverLimit(customerId);
+  if (isOverLimit) {
+    return new Response("Monthly usage limit exceeded", { status: 429 });
+  }
+
+  const { text, usage } = await generateText({
+    model: aiClient(MODEL_ID),
+    maxOutputTokens: 2_000,
+    messages: [
+      {
+        role: "system",
+        content: systemPrompt,
+      },
+      {
+        role: "user",
+        content: makeUserPrompt(sourceLanguage, targetLanguage, type, postTitle, postText, comment),
+      },
+    ],
+  });
+
+  await AIUsage.trackUsage(customerId, MODEL_ID, usage);
+
+  return new Response(text, {
+    headers: { "Content-Type": "application/json" },
+  });
+}